What Makes a Car or Truck Sound Raspy

We have all heard it a car or truck rolls by and we want to cover our ears. It sounds like a swarm of angry bees and we all think the same thing…”what an idiot, but what makes the sound like that. No it is not the supercharger that the person says they have added…in fact a super charger unit would probably make the car quieter. The sound is created by adding an exhaust that has not been tuned for the application.

The exhaust is much more than just a pipe that channels the exhaust gases out of the engine bay. It is a specially tuned system that has been meticulously made for that specific car. The resonant sound that comes from a motor during the combustion process creates a pressure wave which can have a positive or negative effect on the engine depending on how the exhaust is shaped.

The headed is the easiest place to see this effect taking place, when the combustion process ends and the air enters the header. At this point the pressure wave is released as well. It will travel down the pipes and bounce off where ever the header turns into one pipe. When this wave moves back towards the engine it can cause unnecessary force on the now exiting gasses which can lower performance. If the header is built specifically to send this wave to impact the outside of the valves just before they open it will have a positive effect on the system. The early impact will create a low pressure area just outside of the valves and the exhaust can leave the engine more freely. Free flowing exhaust means more HP and better gas mileage. Some people believe that removing the header all together will give better performance but in fact the specifically tuned header creates more horse power than an open system.

The rest of the exhaust system is also tuned the same way, it is all about making sure that pressure waves work for the system as opposed to it. If an exhaust system is attached to a car that is not tuned to control this flow the negative pressure waves and lack of sound deadening material causes this sound. Next time you are in traffic and someone is revving their Nissan Sentra with a huge exhaust, just laugh. Not only do they look like a fool but they have also lowered the performance of their car and lost gas mileage to boot. Not to mention that most cars that are being built now are faster than the cars people tend to “modify”. So you can be happy knowing you can smoke them off the line too. In your stock V6 Camry all the while being comfortable and hitting 30 MPG. 

Is That Smoke Coming From My Tailpipe

It can be a scary experience…not to mention nerve racking. Making that daily commute to work and BOOM a huge cloud of smoke starts to for behind your car. The mind starts to race with all the problems that could be causing this situation is my motor dead, has my turbo gone bad and if so how will it cost to fix my turbocharger. Or the even worse situation, I just replaced the turbo…please not again! The worst part is the install cost like $1000+ and your car will be down again for who knows how long.

When this happens there is always a silver lining to this cloud of smoke, smoke is not always associated with a thousand dollar repair, it can be something much easier. The first step to understanding the issue is to look at the color of the smoke itself. When the smoke is black it is fuel not being burnt correctly, white means that the coolant is burning off and blue means oil is burning.

Now that the color of the smoke can be understood it can be worked out and fixed. When it comes to a newly installed turbo it may be residual oil left from the old turbo’s failure. Oil from a bad turbo will build up in the lowest point in the system and in a turbo intake system that is the intercooler. The intercooler is the unit at the front area of the car where the air travels across to disperse the heat created by the turbocharging process.  When the old oil has pooled in the intercooler the extremely high pressure air can push it into the intake of the car and it will burn off in the engine. Oil smoke is very potent and just one drop can fill up a room with enough smoke to choke someone. It is easy to imagine that a quart of oil would take a long time to burn and will also coat oxygen sensors and valves cause in future issues. The main thing to remember when there is an issue with your car is to take a breath and remember that it is not the end of the world. Even though it may feel that way, if you step back and think it may be something as easy as a coolant hose that has a crack.